Electromagnetic transducer device



May 7, 1963 R. H. BOLTON ELECTROMAGNETIC TRANSDUCER DEVICE 2Sheets-Sheet 1 Filed May 31, 1960 J M E INVENTOR P0555 7 H. 50L r0/vATTORNEY y 7, 1963 R. H. BOLTON 3,089,044

ELECTROMAGNETIC TRANSDUCER DEVICE Filed May 51, 1960 2 Sheets-Sheet 2INVENTOR F I 4 ROBE/FT H 50Lr0/v ATTO NEY aired rates i atet 3,089,044ELEQTROMAGNETKC TRANSDUCER DEVECE Robert H. Bolton, Huntington, N.Y.,assignor to Sperry Rand Corporation, (lreat Neck, N.Y., a corporation ofDelaware Filed May 31, 1960, Ser. No. 32,780 7 Claims. (Cl. 310-36) Thepresent invention relates to an electromagnetic transducer device andparticularly to a combined electromagnetic device which f-unctions as asignal .generator to provide an electrical signal in accordance withmovement between the relative parts thereof and also a torquer toprovide movement between the relative parts thereof in accordance withan electrical signal supplied thereto. The invention is particularlyapplicable to apparatus having sensitive elements, such as gyroscopes.

The disadvantages of prior art electromagnetic transdudcers whenutilized on gyroscopes particularly on floated gyroscopes where thetransducer has a moving iron rotor movable with the gyroscope float orsensitive element include:

(1) Either electrical centering or extremely close machining isrequired.

(2) Radial side forces are always present.

(3) Reaction torques at null, and reaction torques as a function ofangle, are always present.

(4) The linearity of the torquer and the pick-off is severely limited bythe non-linearity of the B-H curve of the core material.

(5) Hysteresis eifects limit torquer accuracy.

(6) Coil winding time constants are quite high.

(7) The torquer requires a fixed field supply.

The present invention overcomes the aforementioned disadvantages and hasthe following advantages over the prior art moving iron rotor devices:

(1) Coercion torques and side forces are substantially eliminated.

(2) Because of its extreme simplicity, it has an unusually high order ofreliability.

(3) The pick-off portion has an extremely high signalto-noise ratiowhich is further improved at higher frequencies because of the greatlyreduced capacity coupling between the primary and secondary. Outputimpedance is very low.

(4) The torquer portion produces extremely linear results withouthysteresis effects and without fixed field circuitry.

(5) The torquer coil time constants are low enough to permit digitaltorquing.

(6) There is a high level of resistance to stray magnetic fields, suchas spin-motor leakage and earths field.

*(7) The pick-off portion can be made to function as a negative springand thereby compensate for elastic restraint torques on the gyroscopefloat.

(8) Limited radial displacements of the gyroscope float do not impairperformance.

It is a primary object of the present invention to provide asubstantially coercion-free electromagnetic transducer device whereinstray magnetic fields have substantially no influence upon the outputprovided thereby.

It is a further object of the present invention to provide anelectromagnetic transducer device having a high order of reliabilitywhich is simple and inexpensive to manufacture and has good linearity ofits output.

It is an additional object of the present invention to provide anelectromagnetic transducer device wherein slight radial displacements ofthe relatively moving parts do not impair the output performance.

The above and other objects are achieved by the combined pick-off andtorquer of the present invention which Patented May '7, 1033 consists ofthree coaxial members comprising an inner stationary stator having anI-shaped core of magnetic material wound with an A.C. excitation coiland symmetrically disposed permanent magnets, all mounted on a commonsupport structure, the curved extremities of which define a circle, anouter hollow cylindrical lamination stack encircling the stator andforming a magnetic flux return path for the pick-oil and the torquer.The lamination stack is in spaced relation with the stator therebyforming an air gap therebetween. A hollow cylindrical sleeve isrotatably disposed in the air gap and supports the pick-oil output coilsand the torquer input coils. In a gyroscope, for example, the stator andthe lamination stack are mounted on the gyroscope housing while therotatable sleeve is connected to rotate with the gyroscope float orsensitive element.

Further objects will appear from the following specification and claimswhen read in conjunction with the drawings in which:

FIG. 1 is a vertical section on an enlarged scale of a gyroscopeincluding the combined pick-off and torquing device of the presentinvention;

FIG. 2 is an end sectional view of the gyroscope of FIG. 1 taken alongline 2-2 of FlG. l and including lines indicating the magnetic fluxpath;

FIG. 3 is a schematic perspective View showing the relationship of thecoils and the stator of the combined pick-off and torquing device; and

FIG. 4 is an exploded perspective view of the elements of the combinedpick-off and torquing device as applied to the gyroscope of FIG. 1.

For purposes of example the present invention will be applied to agyroscope having a floated sensitive element although it will beappreciated that the invention is equally applicable to providingcombined pick-off and torquing functions or individual pick-off ortorquing functions in other applications.

Referring now to PEG. 1, a single-degree-of-freedom integratinggyroscope 10 includes a sensitive element 11 within which a gyro rotor12, shown in dotted lines, is hermetically sealed within a cylindricalfloat 13. The gyroscope ll) has an output or longitudinal axis 14 aroundwhich the sensitive element 11 is rotatable by means of spaced bearings15 and 16 that cooperate with shafts l7 and 13, respectively, the latterextending from opposite extremities of the sensitive element 11. Thebearings 15 and 16 are mounted in spaced end caps 20 and 21,respectively, which form the enclosures for a gyroscopic housing 22. Thehousing 22 is coaxially disposed with respect to the longitudinal axis14 and encloses the sensitive element 11. The gyro rotor 12 spins withinthe float 13 about a horizontal axis 23 that is perpendicular to thelongitudinal axis -14.

The space within the housing 22 between the outer surface of thecylindrical float T3 of the sensitive element 11 and the inner surfaceof the housing 22 is filled with a flotation fluid 25 which surroundsand supports the sensitive element 11. The outer diameter of thecylindrical float i3 is slightly less than the inner diameter of thehollow cylindrical central portion 24 of the housing 22. in order that athin film 26 of flotation fluid 2S therebetween provides the integratingfunction due to the viscous shear eflects of the fluid 25.

The purpose of the gyroscope 10 is to measure rotation about its inputaxis 2'7 and to provide an electrical output signal in response theretohaving an amplitude and phase representative of the amount and directionrespectively of the rotation. When the gyroscope i0 is rotated about itsinput axis 27, a gyroscopic torque is generated about its output axis 1which causes rotation of the floated sensitive element 11 about the axis14- with respect to the housing 22.

To provide an electrical output signal representative of the movement ofthe sensitive element 11 relative to the housing 22 around the axis 14,and to provide means for applying a torque to the sensitive element 11around the axis 14, the gyroscope includes the combined electromagneticpick-off and torquing device 3% of the present invention. The device 3twill now be described with reference to FIGS. 1 to 4. The device 31}includes a stator 31, a rotor 32 cooperative with the stator 31, and acommon magnetic flux return path member 33 as clearly shown in PEG. 4.in the preferred embodiment shown, the stator 31 includes a commonstationary non-magnetic support member 34, an Lshaped core 35 oflaminated magnetic material, first and second A.C. excitation coils 36and 37, respectively, wound on the core 35, and first and secondarcuate-shaped permanent magnets 38 and 39. The stator 31 has itslongitudinal axis coincident with the longitudinal axis 14.

The support member 34 is rigidly connected to the end cap 2d of thehousing 22. The support member 34 has a central opening 42 through whichthe shaft 17 extends in spaced relation with respect to the supportmember 34. The core 35 is mounted on the support member 34 by means ofits central opening 43. The upper and lower extremities 4t} and 41respectively of the core 35 are diametrically opposed and curved forresponse to be explained. The AC. excitation coil 36 is wound around theupper portion of the core 35 while the excitation coil 37 is woundaround the lower portion' of the core 35. The excitation coils 36 and 37are identical and connected to each other in series aiding and alsoconnected to a source of A.C. power 44. The permanent magnets 33 and 39are also mounted on the support member 34 in diametrically opposedrelationship with respect to each other. Preferably, the magnets 33 and39 are identical and symmetrically disposed on opposite sides of thecore 35. The extremities 55 and 56 of the magnet 38 and the extremities5'7 and 58 of the magnet extend outwardly and are curved in orde. thatthey cooperate with the curved extremities 4i and 41 of the core 35 todefine acircle.

The rotor 32 is a hollow cylindrical member that encircles the stator31. The inside diameter of the rotor 32 is slightly greater than thediameter of the circle defined by the curved extremities of the core 35and the magnets 33 and 39 thereby providing a small air gaptherebetween. First and second arcuate-shaped pick-oil coils 45 and 45respectively, and first and second torquer coils 47 and 48 form a partof and are embedded in the rotor 32. As shown in FIG. 3, each of thepick-off coils 45 and 46 consists of two rectangularly wound identicalwire loops 6%, 61 and 62, 63, respectively similar to standard metercoils, connected in series opposition with their winding directionsopposite. The pick-off coils 45 and 46 are series connected to providean additive output signal at the pick-off output terminals 50. Thepick-off coils 45 and 46 are cooperative with the upper and lowerextremities 4t] and 41 respectively of the core 35, as viewed in FIG. 2,to provide a null output from the output terminals 5% when the coils 4-5and 4 6 are centered with respect to the core 35 in a manner to be morefully explained.

The arcuate-shaped torquer coils 47 and 48 are rectangular andcooperative with the curved extremities 55', 56 and 57, 53 of thepermanent magnets 38 and 39, respectively. The coils 47 and 48 areconnected to each other in series aiding relationship and also to a DC.source, such as the battery 51, through a reversing switch 52. The rotor32 is rigidly connected to the sensitive element 11 and coaxial withrespect to the axis 14. With the coils 47 and 43 centered with respectto the magnets 33 and 39 respectively, as shown in FIG. 2, there is notorque produced on the rotor 3 and thus no torque applied to thesensitive element 11 around axis 14 as will be explained more fully. Thecoils 45, 46, 47 and 43 are symmetrically disposed on the rotor 32.

The common magnetic flux return path member 33 comprises a hollowcylindrical lamination stack of magnetic material which encircles aportion of the rotor 32. The flux return path member 33 is stationary byvirtue of its being mounted on the end cap 2%! of the housing 22. Theinside diameter of the return path member 33 is slightly greater thanthe outside diameter of the rotor 32 thereby providing a small air gaptherebetween. The rotor 32 is rotatably disposed in the air gap betweenthe member 33 and the circle defined by the extremities of the core 35and the magnets 38 and 39. Preferably, the member 33 has substantiallythe same dimension in the direction of the axis 14 as the cooperativeportion of the core 35.

In operation, when the gyroscope 10 is initially turned on and theflotation fluid 25 is being heated by conventional means not shown, thesensitive element 11 is prevented from rotating around the output axis14 by more than :10 by means of a slot and key arrangement, not shown.When the flotation fluid 25 reaches a predetermined temperature, thereversing switch 52 is closed to permit current to flow from the battery1 to energize the coils 47 and 48. The direction of the current flow isdependent upon the position of the switch 52 and is determined by thedirection in which it is desired to rotate the sensitive element ll.Depending upon the direction of current flow through the coils 47 and43, the magnetic flux, shown in dotted lines in Flu. 2, induced by theopposed permanent magnets 33 and 39 will be cut by the current in thecoils 47 and 4S producing a force on the rotor 32 which creates a momenton the sensitive element 11 around the axis 14- in a direction to causethe axis 27 to become vertical.

When the sensitive element 11 has its axis 27 vertical, the pick-offcoils 45 and as are centered with respect to the extremities 40 and 41respectively of the core 35. In this condition, the magnetic flux lineslinking each of the loops as, 61, 62 and 63 are equal, as shown in solidlines in FIG. 2, and the voltage induced in the loop 6% is equal andopposite to that induced in the loop 61 since they are connected inseries opposition. Likewise, the voltage induced in the loop 62 cancelsthe voltage induced in the loop 63 thereby providing zero output voltageat the terminals 59.

When the gyroscope 10 is rotated about its input axis 27, the gyro rotor12 will precess causing rotation of the sensitive element 11 around theoutput axis 14. The movement'of the sensitive element 11 carries therotor 32 and the coils 45 and 46 mounted thereon to a new position thatis not centered with respect to the core 35, causing the magnetic fluxlines linking the loops 6%) and 63 to be greater than those linking theloops 61 and 62, for example. This creates an unbalance in the voltageinduced in each of the loops of the coils 45 and 46 resulting in anoutput signal at the terminals 50 having an amplitude and a phaserepresentative of the magnitude and direction of the rotation of thesensitive element 11 from its centered position. Due to the dualarrangement or" the pick-off device, the amplitude of the signal will berepresentative of twice the angle through which the sensitive element 11has rotated.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than of limitation and that changes within thepurview of the appended claims may be made without departing from thetrue scope and spirit of the invention in its broader aspects.

What is claimed is:

1. A combined pick-oil" and torquing device comprising pick-off meansincluding an I-shaped core of magnetic material, an excitation coildisposed on said core,

and first and second output coils cooperative with first and secondextremities respectively of said core, torquing means including firstand second permanent magnets, and first and second input coilscooperative with said first and second magnets respectively, a commonstationary non-magnetic support member for supporting said core and saidmagnets, a common magnetic flux return path member for providing amagnetic flux return path for said pick-off means and said torquingmeans, said flux return path member being in spaced relation withrespect to said core and said magnets thereby defining an air gaptherebetween, and a common movable element disposed within said air gapsupporting said pick-oil. output coils and said torquer input coils formovement relative to said core and said magnets.

2. A combined piclooif and torquing device comprising pick-elf meanshaving I-shaped laminated core of magnetic material, A.C, excitationcoil means Wound on said core, and first and second output coilscooperative with first and second extremities respectively of said core,torquing means having first and second permanent magnets, and first andsecond D.C. excitation input coils cooperative with said first andsecond magnets respectively, a common stationary non-magnetic supportmember for supporting said core and said magnets, a common laminatedmagnetic flux return path member for providing a magnetic flux returnpath for said pick-off means and said torquing means, said flux returnpath member being in spaced relation with respect to said core and saidmagnets thereby defining an air gap therebetween, and a common movableelement disposed within said air gap supporting said pick-01f outputcoils and said torquer input coils for movement relative to said coreand said magnets.

3. A combined pick-off and torquing device comprising pick-elf meanshaving an l-shaped core of magnetic material, A.C. excitation coilswound on said core, and first and second output coils cooperative withfirst and second extremities respectively of said core, torquing meanshaving first and second arcuate-shaped permanent magnets and first andsecond D.C. excitation input coils cooperative with the extremities ofsaid first and second magnets respectively, the extremities of said coreand said magnets being symmetrically disposed and curved to therebydefine a circle, a common stationary non-magnetic support member forsupporting said core and said magnets, said support member having alongitudinal axis, a common circular magnetic flux return path memberfor providing a magnetic flux return path for said pick-off means andsaid torquing means, said flux return path member being in spacedrelation with respect to said core and said magnets thereby defining acircular air gap therebetween, and a common circular rotatable elementdisposed within said air gap supporting said pick-off output coils andsaid torquer input coils for rotation relative to said core and saidmagnets around said longitudinal axis, said rotatable magnetic elementand said flux return path member being coaxially disposed with respectto said longitudinal axis.

4. A symmetrical combined pick-ofi and torquing device comprisingpick-off means having an I-shaped core of magnetic material, A.C.excitation coil means wound on said core, and first and secondarcuate-shaped output coils cooperative with first and secondextremities respectively of said core, torquing means having first andsecond arcuate-shaped permanent magnets, and first and secondiarcuate-shaped input coils cooperative with the extremities of saidfirst and second magnets respectively, the extremities of said core andsaid magnets being symmetrically disposed and curved to thereby define acircle, common stationary nonma netic support member for symmetricallysupporting said core and said magnets, said support member having alongitudinal axis, a common hollow cylindrical magnetic flux return pathmemher for providing a magnetic flux return path for said pick-off meansand said torquing means, said flux return path member being disposedcoaxially with respect to said longitudinal axis and in spaced relationwith respect to said circle thereby defining a circular air gaptherebetween, and a common hollow cylindrical rotatable elementcoaxially disposed within said air gap supporting said picloofif outputcoils and said torquer input coils for rotation around said longitudinalaxis, said coils being symmetrically disposed on said element.

5. A combined pick-off and torquing device comprising a pick-0d having acore of magnetic material, an excitation coil wound on said core and anoutput coil cooperative with said core, a torquer having a permanentmagnet and an input coil cooperative with said permanent magnet, acommon stationary non-magnetic support member for supporting said coreand said magnet, a common magnetic flux return path member for providinga magnetic flux return path for said pick-off and said torquer, saidflux return path member being in spaced relation with respect to saidcore and said magnet thereby defining an air gap, and a common movableelement disposed in said air gap supporting said pick-off output coiland said torquer input coil for movement relative to said core and saidmagnet.

6. A pick-off device comprising an I-shaped stationary core of magneticmaterial, an A.C. excitation coil disposed on said core, first andsecond output coiis cooperative with first and second extremitiesrespectively of said core, said core having a longitudinal axis, astationary hollow cylindrical magnetic flux return path member forproviding a magnetic flux return path for said picleoif, said memberbeing disposed in spaced relation with respect to said core extremitiesthereby defining an air gap, and a rotatable hollow cylindrical elementdisposed in said air gap supporting said output coils for rotationaround said axis relative to said core whereby an output signal isprovided from said output coils having an amplitude and phaserepresentative of the extent and direction of the movement of saidelement with respect to said core.

7. A torquing device comprising a stationary nonmagnetic support memberhaving a longitudinal axis, first and second arcuate-shaped permanentmagnets mounted in opposed spaced relation on said support member, firstand second excitation coils cooperative with the extremities of saidfirst and second magnets respectively, a stationary hollow cylindricalmagnetic flux return path member for providing a magnetic return pathfor said torquing device, said member being disposed in spaced relationwith respect to said magnet extremities thereby defining an air gap anda rotatable hollow cylindrical element disposed in said air gapsupporting said excitation coils for rotation around said axis relativeto said magnets whereby a torque is applied to said element inaccordance with the magnitude and direction of excitation supplied tosaid coils.

References Cited in the file of this patent UNITED STATES PATENTS

3. A COMBINED PICK-OFF AND TORQUING DEVICE COMPRISING PICK-OFF MEANSHAVING AN I-SHAPED CORE OF MAGNETIC MATERIAL, A.C. EXCITATION COILSWOUND ON SAID CORE, AND FIRST AND SECOND OUTPUT COILS COOPERATIVE WITHFIRST AND SECOND EXTREMITIES RESPECTIVELY OF SAID CORE, TORQUING MEANSHAVING FIRST AND SECOND ARCUATE-SHAPED PERMANENT MAGNETS AND FIRST ANDSECOND D.C. EXCITATION INPUT COILS COOPERATIVE WITH THE EXTREMITIES OFSAID FIRST AND SECOND MAGNETS RESPECTIVELY, THE EXTREMITIES OF SAID COREAND SAID MAGNETS BEING SYMMETRICALLY DISPOSED AND CURVED TO THEREBYDEFINE A CIRCLE, A COMMON STATIONARY NON-MAGNETIC SUPPORT MEMBER FORSUPPORTING SAID CORE AND SAID MAGNETS, SAID SUPPORT MEMBER HAVING ALONGITUDINAL AXIS, A COMMON CIRCULAR MAGNETIC FLUX RETURN PATH MEMBERFOR PROVIDING A MAGNETIC FLUX RETURN PATH FOR SAID PICK-OFF MEANS ANDSAID TORQUING MEANS, SAID FLUX RETURN PATH MEMBER BEING IN SPACEDRELATION WITH RESPECT TO SAID CORE AND SAID MAGNETS THEREBY DEFINING ACIRCULAR AIR GAP THEREBETWEEN, AND A COMMON CIRCULAR ROTATABLE ELEMENTDISPOSED WITHIN SAID AIR GAP SUPPORTING SAID PICK-OFF OUTPUT COILS ANDSAID TORQUER INPUT COILS FOR ROTATION RELATIVE TO SAID CORE AND SAIDMAGNETS AROUND SAID LONGITUDINAL AXIS, SAID ROTATABLE MAGNETIC ELEMENTAND SAID FLUX RETURN PATH MEMBER BEING COAXIALLY DISPOSED WITH RESPECTTO SAID LONGITUDINAL AXIS.